1. Technical Field
The present invention pertains to an igniter for igniting explosives for pyrotechnic or high explosive charges.
2. Description of Related Art
As discussed in U.S. Patent Application Publication No. 2004/0231546, detonators are used to initiate various types of explosive charges from industrial to military settings. Some detonation systems utilize electrical current to initiate the explosive charge. These electric detonators typically consist of an elongated shell with an electrical ignition element at one end and an explosive base charge enclosed at the other end. External initiator leads extend through the ignition element and into the detonator interior, facing towards the base charge. A small bridge wire extends across the ends of the initiator leads and is usually covered with a small amount of explosive material. To detonate the device, electrical current is introduced across the initiator leads. The small diameter of the bridge wire creates resistance to the flow of electrical current, generating heat. If the heat exceeds a critical temperature, the explosive material reacts, initiating the explosive reaction that will ultimately cause the detonation of the base charge. Additionally, a delay element may be disposed between the ignition element and the base charge to regulate the time between the initiation of the explosive reaction and the detonation of the base charge.
The design of electric detonators utilizing the heating of a bridge wire allows low electrical current signals to be employed. This creates safety issues regarding the premature detonation of these devices. One of these issues relates to static electricity buildup. Static electricity from the environment or the individual using the detonator may build up in the initiation leads and be discharged through the bridge wire, causing premature initiation of the explosive reaction and the detonation of the base charge.
Another major safety issue involved with electric detonators concerns RF radiation from radios and cell phones. If the length of the initiator leads is a multiple of the wavelength of the RF radiation, the leads may act as antennas, causing a small current to flow through the bridge wire. This absorbed energy can cause incidental heating of the bridge wire in conventional detonators and initiate the explosive reaction. Advantages over conventional bridge wire igniters or primers are described in U.S. Pat. No. 5,235,127 and U.S. Pat. No. 6,205,927. Although such devices provide certain advantages set forth therein, there is a need for an igniter that can be easily manufactured and used in a variety of applications permitted by a flexible igniter.